Home Builders Institute Pre-Apprenticeship Certificate Training (HBI-PACT) Practice Test

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Which material is used in fire extinguishers listed in the context?

CO2
Water
Dry Chemical
Foam

The correct answer is: CO2

The use of CO2, or carbon dioxide, in fire extinguishers is particularly effective for Class B (flammable liquids) and Class C (electrical) fires. CO2 extinguishers work by displacing oxygen in the area of the fire, effectively suffocating the flames and preventing re-ignition. They are advantageous because they leave no residue, making them suitable for use on delicate equipment, such as computers or electrical machinery. In contrast, water is primarily used for Class A fires (ordinary combustibles like wood, paper, and cloth) and can be ineffective or even dangerous for other classes of fire. Dry chemical extinguishers are versatile and can handle multiple classes of fire but leave a residue that may be harmful to sensitive equipment. Foam extinguishers are primarily effective on Class A and B fires but are not as effective as CO2 for protecting against electrical fires. Therefore, carbon dioxide is specifically highlighted for its unique properties and effectiveness in certain fire types, making it a crucial option in fire safety equipment.